Formalin-Fixed Paraffin Embedded (FFPE) Tissue Preservation: A Method for Studying Tissue Morphology

- First, place a tissue slice on a filter paper soaked with PBS to prevent cell shrinkage or swelling by balancing osmolarity. Transfer the tissue to a histo cassette. Close and place the cassette in neutral buffered formalin, NBF solution. NBF contains formaldehyde that binds to amino groups of amino acids and prevents formic acid formation that pigments the tissue. Leave the cassette overnight at a low temperature, which prevents nucleic acid degradation and fixes the tissue. Dehydrate the tissue with multiple washes of alcohol.

Place it in liquid paraffin and press it down to the mold's bottom. Remove the weight and place the bottom of the histo cassette on the tissue. Pour liquid paraffin on the assembly. Allow the setup to solidify on a cold plate. Paraffin is insoluble in water, and after entering the dehydrated tissue it hardens and helps in sectioning. Transfer the tissue block on a microtome. Cut and collect thin sections of the tissue on a slide. If the section is too thick, oxygen and other nutrients cannot diffuse across the slice creating a false necrosis gradient. If the section is too thin, then it tends to curl. The protocol video examines biomarker expression and c